1. Living or growing partly on land and partly in water: "A marginal subaquatic flora."
2. Growing or remaining under water.
3. Being under water, or beneath the surface of water; adapted for use under water; such as, a submarine or a subaqueous helmet.
4. Formed in or under water; such as, "subaqueous deposits".
5. The practice of going underwater with or without a breathing apparatus.

When done for sport, this is sometimes called subaquatics. There are different kinds of underwater diving.

Snorkeling and free diving: swimming underwater without a breathing apparatus. An apparatus used by swimmers and skin divers, consisting of a long tube held in the mouth.

Recreational diving and professional diving (commercial diving, diving for scientific research purposes or diving for financial gain) takes a range of diving activities to the underwater work site: "Subaquatics involves competitive sports using either free-diving, snorkeling, scuba techniques, or a combination of these techniques."

1. Of or relating to latitudes just south of the Arctic Circle as in landscape or weather conditions.
2. Those regions of the Northern Hemisphere associated with taiga or subarctic climates, having temperatures below freezing for over half the year but often over 80 degrees Fahrenheit during the summer.

1. The act of understanding a word or thought that is implied but not actually expressed in speech or writing.
2. A word, idea, or thought understood by a hearer or reader that is implied but not expressed.